The present invention relates to a dryer section of a paper making machine. The dryer section is made up of a plurality of dryer groups. Each group is comprised of a series of heated dryer cylinders with each cylinder followed by a reversal roll, typically with a suction capability. The web travels through each dryer group in a meander path, over one side, e.g. the top, of a dryer cylinder and over the opposite side, e.g. the bottom, of the next reversal roll, over the one side of the next dryer cylinder., etc. A continuous endless loop supporting belt, e.g. a porous dryer felt or a screen-like dryer fabric screen travels with the web through each dryer group. Prior art on such a dryer section is represented by FIG. 1 of International Application WO 88/04206 and by U.S. Pat. No. 5,065,529.
Dryer sections of this type are intended for drying a fibrous web, e.g. a paper web, especially in a paper making machine designed to run at very high speeds, on the order of 1000-2000 m/min. One requirement for such a dryer section is that the web travel through the machine as reliably as possible without tearing, despite its extremely high speed. In other words, the runability must be very high. The fibrous web and its supporting belt are advanced through the dryer section with the aid of the reversal suction rolls between the dryer cylinders. Critical points are where the web, resting on the supporting belt, e.g. the dryer felt, leaves its direct contact with a dryer cylinder to move to the suction roll that follows. Another requirement is that the dryer cylinders dry the web as effectively as possible so that only a reasonable number of cylinders will be needed despite the extremely high web speed. When fewer dryer cylinders are employed, the entire dryer section can be shorter.